1. Field of the Invention
The present invention relates to a polycrystalline silicon layer, a flat panel display using the same, and a method of fabricating the same, and more particularly, to a polycrystalline silicon layer, a flat panel display using the same, and a method of fabricating the same in which a predetermined region of an amorphous silicon layer is crystallized by a super grain silicon (SGS) crystallization technique, crystallinity of a seed region is spread to become a crystallization layer, and then the crystallization layer is formed as a semiconductor layer. The resulting polycrystalline silicon layer has excellent characteristics and uniformity.
2. Description of the Related Art
A thin film transistor used in a flat panel display, such as an organic electro luminescence device, is made by depositing an amorphous silicon layer on a transparent substrate such as a glass, quartz or plastic substrate, dehydrogenating the amorphous silicon layer, ion-implanting impurities for forming a channel, crystallizing the amorphous silicon layer to form a polycrystalline silicon layer, and then patterning the polycrystalline silicon layer to fabricate a semiconductor layer.
Methods of crystallizing the amorphous silicon layer into a polycrystalline silicon layer include solid phase crystallization (SPC), excimer laser crystallization (ELC), metal induced crystallization (MIC), and metal induced lateral crystallization (MILC). SPC is a method of annealing an amorphous silicon layer for several to several tens of hours at a temperature of about 700° C. or less, which is a transition temperature of glass used as a substrate of a display device employing a thin film transistor. ELC is a method of crystallizing a silicon layer by irradiating the silicon layer with an excimer laser and locally heating the silicon layer to a high temperature for very short time, and MIC is a method of using phase transfer induction from amorphous silicon to polysilicon by contacting the amorphous silicon layer with metals such as nickel (Ni), palladium (Pd), gold (Au), and aluminum (Al), or implanting such metals into the amorphous silicon layer. MILC involves a technique of inducing sequential crystallization of silicon by lateral diffusion of silicide formed by reacting metal with the silicon.
However, when thin film transistors are made of the polycrystalline silicon layers crystallized by these methods, the thin film transistors have non-uniform characteristics such as non-uniform threshold voltage and off-characteristics due to non-uniform grain size and irregular distribution of grain boundaries.